The present invention relates to a capacitive type pressure sensor for detecting fluid pressure, and particularly to a construction of a pressure sensor used for controlling an engine of vehicle and a method of manufacturing the sensor utilizing a semiconductor micro-machining technology.
As a conventional pressure sensor, pressure sensors are disclosed, for example, in Japanese Patent Publication No.62-502645 and Japanese Patent Laid-open No.6-252420.
Japanese Patent Publication No.62-502645 proposes a construction of a pressure sensor and a method of manufacturing the sensor. The pressure sensor is composed of a semiconductor substrate; a solid material having a central portion capable of being deformed, the central portion being arranged on the substrate though a cavity, a peripheral portion bonded to the substrate and an etch channel portion extending to the central portion through the peripheral portion; and a material for sealing the etch channel.
Japanese Patent Laid-open No.6-252420 proposes a pressure sensor which comprises a first electrode which is formed by doping a surface of a semiconductor substrate; a second electrode made of a polycrystalline diaphragm which is made conductive by doping, the second electrode being arranged above the first electrode; a cavity formed between the first and the second electrodes; and a plug for sealing the cavity selectively deposited in an opening portion which is formed so as to penetrate a layer of the diaphragm, wherein the second electrode of diaphragm is deformed by a pressure difference between the diaphragm cavity and the external, and a change in electric capacitance due to the deformation is detected.